In machine tools the presence of contaminants on tool contact surfaces can result in a suboptimal clamping of tools. Contaminants can consist, in particular, of metal chips that unavoidably occur in the machining of a workpiece. Consequently, defective machining can result from a tilted position or an axial offset of the tool. This effect is further intensified by the use of long tools. To improve the manufacturing quality and reduce the proportion of rejects, it is desirable to be able to recognize the occurrence of faulty tool clamping before machining begins. Therefore, it has already been suggested that the quality of tool clamping in machine tools be checked by monitoring the planar abutment of the tool.
For machine tools, there is also the need to monitor the position of various machine elements. An example of this is the drive for actuating the tool chuck. A position measurement on an element of this drive is suitable for providing information as to whether or not control commands from the machine controller for loosening or tightening a tool are executed correctly.
DE 103 51 347 A1 describes the monitoring, by means of pressure-sensitive, tension-sensitive or force-sensitive sensor apparatus, of the forces appearing at the chuck of a machine tool. The objective pursued in this case is the simultaneous monitoring of the correct tool tension and the forces appearing during machining, in order to be able to optimize the process parameters during machining For this purpose, the sensors must be integrated into the chuck in such a manner that they are included in the flow of force occurring during machining
DE 199 59 778 A1 teaches the use of a telemetry system with a distance-measuring sensor apparatus for simultaneous checking of the clamping state and the planar abutment of the tool on the spindle. The document does not contain any detailed information on the configuration of the sensor apparatus and the telemetry unit, however.
DE 199 03 183 A1 describes a high-frequency distance measuring device with an antenna constructed as a sensor and a waveguide open at one end, the open end of which is terminated with a damping member. A reflective object whose position is to be determined is situated in the vicinity of the damping member. The transmission frequency of the oscillator is regulated such that the arrangement is resonant. The resonant frequency is a measure of the distance of the reflecting object from the damping member. Various applications are suggested, in which the distance sensor is always installed in the interior of a mechanical device, in which a distance measurement is to be performed at one of its components.
The problem of the invention is to create a new and expedient solution that can be easily and economically realized for monitoring the position of a tool or machine element on or in a work spindle or tool chuck, in particular, in a machine tool.
This problem is solved according to the invention by a device with the characteristics of Claim 1. Advantageous configurations are specified in the subordinate claims.